Evaluation of a mouse monoclonal antibody for the determination of serum theophylline by fluorescence polarization immunoassay

Theophylline concentrations in spiked human serum and serum specimens obtained from patients with normal and impaired renal function were measured by fluorescence polarization immunoassay (FPIA) using a mouse monoclonal antitheophylline antibody. The interday coefficients of variation of the assay after 14 days were 4.2, 3.3, and 2.4% at serum theophylline concentrations in pooled human serum of 7.1, 12.2 and 26.9 mg/L. Theophylline concentrations determined by FPIA and high performance liquid chromatography (HPLC) were used to generate the following linear regression equations relating the corresponding theophylline concentrations measured by each method in serum specimens from 50 patients with normal renal function (FPIA = 1.00 HPLC + 1.01, r = 0.98) and 50 patients with end-stage renal disease (FPIA = 1.04 HPLC + 0.08, r = 0.99). In contrast to previous studies performed with a polyclonal antitheophylline antibody, the precision, accuracy, and specificity of the FPIA were adequate for analysis of theophylline in serum specimens obtained from patients with end-stage renal disease.

The effects of prenatal methylazoxymethanol acetate (MAM) on holeboard exploration and shuttle avoidance performance in rats

Forty pregnant rats were given an IP injection of either 0, 14, 22, or 30 mg/kg of MAM on day 15 of gestation. One animal of each sex from each litter was tested between 80 and 90 days of age in a holeboard mounted on a stabilimeter. An additional animal of each sex from each litter was tested between 110 and 120 days of age in a two-way shuttle avoidance task. In the holeboard task, prenatal treatment with MAM resulted in an increased frequency of dipping which was accompanied by an increased number of transitions between holes, rather than stereotypy. Altered patterns of exploratory behavior over the course of the test session were also evident in MAM treated offspring as compared to controls. The 22 mg/kg group tended to show less of a decrease in their activity levels over the course of the session than the other groups. In the shuttle avoidance task, prenatal treatment with MAM resulted in a facilitation of avoidance performance as compared to controls. In addition, increased activity (as measured by intertrial interval crossings) was evident in MAM treated offspring, while escape latencies were equivalent across the groups. However, the pattern of results suggest that the facilitated avoidance performance cannot be accounted for by the increased activity. These results are discussed in terms of various hypothesis which may account for the behavioral deficits shown by MAM treated offspring.

Protein binding of disopyramide--displacement by mono-N-dealkyldisopyramide and variation with source of alpha-1-acid glycoprotein

The binding of disopyramide to human serum proteins and human alpha-1-acid glycoprotein (AAG) was determined over a wide drug concentration range. Addition of 3.7 X 10(-6) mol litre-1 mono-N-dealkyldisopyramide caused a 20-100% increase in disopyramide free fraction. The disopyramide free fraction in AAG solutions prepared from various commercially available sources of alpha-1-acid glycoprotein varied up to 2.5 fold at corresponding disopyramide concentrations. Pronounced differences in the calculated binding constants (affinity and capacity) were observed among the commercially available AAG preparations. These findings suggest that binding studies should be performed in appropriately harvested human serum or plasma to avoid possible artifacts associated with the use of commercial preparations of alpha-1-acid glycoprotein for binding studies.

Laser therapy of coronary artery obstructions

Laser energies can be transmitted through flexible optical fiber to vaporize and penetrate coronary atherosclerotic and thrombotic obstructions. There are risks and complications involved in this therapy, however, including perforation, aneurysm formation, and thromboembolic risks, and further research is needed to render the laser recanalization procedure safe.

Phosphorus-31 nuclear relaxation rate studies of the nucleotides on phosphoenolpyruvate carboxykinase

The interactions of nucleotide substrates with the enzyme phosphoenolpyruvate carboxykinase and its Mn2+ complex were investigated by several methods. Direct binding shows the formation of stoichiometric complexes. The presence of Mn2+ increases the affinity of the enzyme for nucleotide. A higher affinity for GTP (Kd less than 2 microM) than for GDP (Kd = 15 microM) was determined. Solvent proton relaxation rate studies indicate no substantial difference in titration curves for free nucleotide or for Mg-nucleotide to the enzyme-Mn complex. The effect of Mn2+ on the 31P relaxation rates of IDP and of ITP in the binary Mn-nucleotide complex indicates the formation of direct coordination complexes. The distances of the alpha- and beta-31P of IDP to Mn2+ are identical (3.5 A). The Mn2+ distance to the beta- and gamma-31P of ITP is also identical (3.7 A) and is 0.2 A further from the alpha-phosphorus. In the presence of P-enolpyruvate carboxykinase, the effect of Mn2+ on the 31P relaxation rates was measured at 40.5 MHz and at 121.5 MHz. The dipolar correlation time was calculated to be 0.6-5.4 ns, depending upon assumptions made. The Mn2+ to phosphorus distances indicate the nucleotide substrates form a second sphere complex to the bound Mn2+. From 1/T2 measurements, electron delocalization from Mn2+ to the phosphorus atoms is indicated; this effect occurs although direct coordination does not take place. The exchange rate of GTP from the enzyme-Mn complex (koff = 4 X 10(4) s-1) is rapid compared to kcat with a lower energy of activation (9.2 kcal/mol) than for catalytic turnover.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of laser radiation on the morphology of human coronary atherosclerotic disease

Laser energy delivered through optical fibers can produce potent controlled thermal dissolution of human coronary obstructive disease, thus widening the stenotic vascular lumen. The ease of vaporization and penetration depends not only on the physical properties of the laser beam but also on the physical characteristics of the atherosclerotic plaque. Lipid-laden plaques are more easily vaporized compared with plaques that are heavily calcified. In atherosclerotic animal models studied in vivo, laser radiation produced a charred lining around the evacuated area and rapid regeneration of a new endothelial lining. After several weeks, the laser-induced crater was still evident, and thrombogenesis was not a significant complication. Focal aneurysmal dilatation may develop when there is thermal injury of the medial layer, and acute perforation can occur if severe laser burn is extended beyond the adventitial layer. Further technical advances and achievements are needed before laser recanalization becomes a clinical reality.

EEG and seizure threshold in normal and lissencephalic ferrets

Changes in EEG and susceptibility to electrically induced seizures were examined in the ferret with lissencephaly produced by exposure to a single injection of methylazoxymethanol acetate (MAM Ac) given to the pregnant jill on gestation day 32. Ten lissencephalic and 11 normal ferrets were chronically implanted with 14 cortical stainless steel electrodes. EEG records were sampled from various stages of the sleep/awake cycle. Six of each group were subjected to electrical stimulation for seizure threshold. Although the number of stimulations and the current intensity required to produce epileptiform afterdischarges (AD) and seizures were not different between the two groups, the lissencephalic ferrets had significantly longer AD and seizures, and a greater number of generalized seizures, indicating an enhanced seizure susceptibility. The EEG of the lissencephalic ferrets was characterized by increased slow wave activity within the low theta band range, extreme spindle activity, focal or multifocal slow and sharp waves, spikes, or spike and slow wave complexes. The differences in the EEG were more pronounced during drowsiness and sleep stages. The brains of all of the treated animals were lissencephalic and hydrocephalic, and weighed significantly less than those of the normals. The cerebral cortex was thin and flattened, with the parieto-occipital region most severely affected. Heterotopic foci were found in the cerebellum as well as in the cerebral cortex. Abnormalities in the configuration of the cerebellar folia were also seen. Comparison between the electrophysiological and neuropathological data suggests that the extent of the extreme spindle activity, and longer AD and seizure duration depended on the degree of cerebellar dysplasia, whereas the EEG focal abnormalities were related to lesions in the cerebral hemispheres.

A farmworker death due to pesticide toxicity: a case report

In the state of California, the use of pesticides is closely regulated. Physicians are required to report all occupational illness attributable to pesticide use. The case of a death involving the handling of aldicarb, a potent methylcarbamate insecticide, is presented. Although the autopsy indicated trauma as the cause of death, subsequent analysis of tissue residues of aldicarb and its metabolites suggested that pesticide toxicity may have been a contributing cause.

Restriction endonuclease mapping of the frog virus 3 genome

A physical map for the frog virus 3 (FV 3) genome was constructed after digestion with the following restriction endonucleases: EcoRI, HindIII, KpnI, and XbaI. Mapping of the DNA was accomplished by partial digestion and recutting, double-digestion, and Southern blot hybridization with deduction of overlaps. Although the virion DNA is physically linear, the restriction map was circular, supporting the data that the FV 3 genome is circularly permuted (Goorha and Murti, Proc. Nat. Acad. Sci USA 79, 248-252, 1982), a unique feature among eukaryotic viruses.

Combination chemotherapy with Clostridium perfringens phospholipase C and cytosine antimetabolites: complementary inhibition directed at membrane lipids

Tumor cell membranes were susceptible to the action of Clostridium perfringens phospholipase C, and this was reflected by inhibition of cellular replication in culture. The differential susceptibility of two neoplastic cell lines to this enzyme was studied in detail. The growth of sarcoma 180 cells cultured in Fischer's medium was markedly inhibited by phospholipase C; whereas, in contrast, cultured L1210 leukemia cells were relatively resistant to the cytotoxic effects of this enzyme. The differential sensitivity of these two neoplastic cell lines to phospholipase C was corroborated by dye-exclusion tests. Thus, leukemia L1210 cells exposed to a concentration of 0.2 mg of phospholipase C per ml of Fischer's medium for 30 min at 37 degrees C were able to exclude Trypan Blue; whereas, only about 21% of sarcoma 180 cells treated under identical conditions were able to exclude the dye. That the cytotoxicity of phospholipase C to sarcoma 180 was the result of hydrolysis of phospholipids of the plasma membrane was supported by measurements of the rate of hydrolysis of radioactivity from the phospholipid of neoplastic cells prelabeled with [3H]choline. Eighty-two percent of incorporated radioactive choline was released from sarcoma 180 cells treated with phospholipase C in Fischer's medium, whereas, only 20% of the label from [3H]choline was solubilized from L1210 leukemia cells treated with the enzyme under similar conditions. Scanning electron microscopy revealed significant damage to sarcoma 180 cells exposed to phospholipase C in Fischer's medium, which was characterized by alterations in size and shape of cells, disappearance of microvilli, and appearance of fistulas in cell membranes; relatively resistant L1210 leukemic cells did not appear to be markedly damaged by comparable enzyme treatment. Exposure of leukemia L1210 cells to phospholipase C in Puck's saline A increased the sensitivity of these cells to enzymatic action. Under these conditions, a comparable amount of phospholipid was hydrolyzed from surface membranes of sarcoma 180 and leukemia L1210 cells, and the degree of membrane damage appeared to be similar, as measured by the capacity of the tumor cell lines to exclude Trypan Blue and by scanning electron microscopy. The extensive damage to membranes by hydrolysis of phospholipids was not accompanied by a change in the degree of specific binding of [3H]concanavalin A(ConA).(ABSTRACT TRUNCATED AT 400 WORDS)

Solubilization of murine melanoma xylosyltransferase and galactosyltransferase activities and their inactivation by dialdehyde nucleosides

The enzymes involved in the initial steps in the biosynthesis of glycosaminoglycans were examined in the murine B16 melanoma. Approximately 60% of the melanoma xylosyltransferase activity and nearly all of the galactosyltransferase activity were membrane-bound; these enzymatic activities were solubilized by treatment with Nonidet P-40 and potassium chloride, and the Michaelis constants for the substrates and acceptor molecules were determined and found to be comparable to those reported for these enzymes from the chick embryo and a rat chondrosarcoma. Dialdehyde nucleosides, which have been reported to alter the activity of several enzymes involved in nucleic acid synthesis, inhibited both xylosyltransferase and galactosyltransferase activities, with galactosyltransferase being considerably less sensitive than xylosyltransferase. The inhibition of xylosyltransferase by dialdehyde nucleosides was irreversible, with no apparent specificity for the base moiety of the dialdehyde nucleosides.

The role of cations in avian liver phosphoenolpyruvate carboxykinase catalysis. Activation and regulation

The activation of the avian liver phosphoenolpyruvate carboxykinase catalyzed reversible decarboxylation of oxalacetate by Mn2+ has been studied. The Mn2+ facilitates the interaction of oxalacetate to the enzyme. At saturating ITP and oxalacetate concentrations, Mn2+ has a Km = 2 microM. The cation Mg2+ can substitute for Mn2+ with 50% Vmax in the oxalacetate decarboxylation and 2% Vmax in the oxalacetate formation. The Km for Mg2+ is 3 orders of magnitude greater than the Km of Mn2+, however. Of the other cations tested (Ca2+, Zn2+, Fe2+, and Cd2+), Co2+ was the only other cation found to activate the enzyme in both directions. In the presence of Mg2+, the enzyme is extremely sensitive to trace metal contaminants which can cause activation. At 1 mM Mg2+, 20 microM Mn2+ causes a 15-fold activation of activity. The apparent Km for Mn2+ (2 microM) at high concentrations of Mg2+ is the identical value calculated for free Mn2+. In a mixed metal (Mg2+ and Mn2+) assay, the Km values for phosphoenolpyruvate and for oxalacetate are independent of the concentration of Mg2+ but decrease upon an increase in Mn2+. The kinetic results demonstrate two roles for the divalent cations for activity. The cation forms a metal . nucleotide complex which serves as the substrate. The results indicate that MgITP is a better substrate than MnITP, but MnIDP is a better substrate than MgIDP. The cation also binds to the enzyme to form an enzyme . metal complex which is the active form of the enzyme. This cation functions to aid in the interaction of either oxalacetate or phosphoenolpyruvate to the enzyme. The activation by micromolar amounts of Mn2+ at millimolar concentrations of Mg2+ suggests that this enzyme, and thus the pathway of gluconeogenesis, can be modulated by changes in concentration of Mn2+ within mitochondria.